Somehow name the gas (7)
I believe the answer is:
methane
'gas' is the definition.
(methane is a gas)
'somehow name the' is the wordplay.
'somehow' indicates anagramming the letters.
'name'+'the'='namethe'
'namethe' anagrammed gives 'METHANE'.
(Other definitions for methane that I've seen before include "Get fuel" , "contributor to global warming" , "Main constituent of natural gas" , "Naturally occurring flammable gas" , "Greenhouse gas produced by cows" .)